Ultrafine-grained (UFG) nanostructured materials having grain sizes of tens and hundreds of nanometers recently have aroused interest among researchers in the materials science field. With respect to their mechanical properties, one would hope to be able to obtain the extremely strong states that can be expected in the case of strong grain refinement according to the Hall-Petch relationship (Gl...

9 = 0.6 I / s ' 7 = 6.0 0 7 = 2 4 i ti 3 = 6 0 Through close control over green-state powder processing, pure alumina ceramics of 0.5-pm grain size were obtained by sintering at 1250°C. The static grain growth of this material was modest at temperatures below 1300°C. However, dynamic grain growth occurred rapidly during superplastic deformation. Therefore, although the ultrafine-grained alumina...

Formation of nano/ultrafine grain structure in AISI 304L austenitic stainless steel through the martensite reversion treatment was studied. The solution annealed specimens were cold rolled up to 95 % thickness reduction at -15°C. The cold-rolled specimens were subjected to reversion annealing treatment at the temperature range of 700-1000 °C for 10–150 min. Microstructural evolutions were analy...

A microstructure consisting of ultrafine grained (UFG) ferrite with average grain size of ~ 0.7 µm and dispersed nano-sized carbides was produced by cold-rolling and tempering of the martensite starting microstructure in a low carbon steel. Subsequently, fine grained dual phase (DP) steel consisting of equiaxed ferrite grains with average size of ~ 5 µm and martensite islands with average size ...

Microstructure, texture and tensile properties of ultrafine/nano grained 1 magnesium alloy processed by accumulative back extrusion 2 3 S.M. Fatemi, A. Zarei-Hanzaki, J.M. Cabrera 4 5 a School of Mechanical Engineering, Shahid Rajaee Teacher Training University, 136-16785, Tehran, Iran 6 b Department of Metallurgical & Materials Engineering, University of Tehran, 515-14395, Tehran, Iran 7 c Dep...

The formation of nano/ultrafine grained ferrite in low carbon steels containing different amounts of niobium was investigated using thermomechanical treatment which consisted of annealing of 85% cold rolled martensite with different parameters. The specimens were characterized by optical and scanning electron microscopy and Vickers hardness test. A lamellar dislocation cell structure was formed...

Blending ultrafine-grained microstructure with other added reinforcement elements that can provide good strength-microstructural integrity is the primary metallurgical target for any developed composite to exhibit its maximum strength at reduced cost and energy in aerospace application. Such nano-reinforced aluminium alloy composites are processed through addition of nano alumina using powder m...

This work has two primary goals. The first is to advance our fundamental understanding of grain boundaries by making direct measurements of grain boundary thermodynamic properties using ultrafine-grained materials. The second is to explore possible deviations from conventional behavior at ultrafine grain sizes, specifically in regards to grain boundary thermodynamic properties and solute segreg...

An ultrafine/nano grained AZ31 magnesium alloy was produced through four-pass ECAP processing. TEM microscopy indicated that recrystallized regions included nano grains of 75 nm. Pole figures showed that a fiber basal texture with two-pole peaks was developed after four passes, where a basal pole peak lies parallel to the extrusion direction (ED) and the other ~20° away from the transverse dire...

Dynamic recrystallization (DRX) is an important grain refinement mechanism to fabricate steels with high strength and high ductility (toughness). The conventional DRX mechanism has reached the limitation of refining grains to several microns even though employing high-strain deformation. Here we show a DRX phenomenon occurring in the dynamically transformed (DT) ferrite, by which the required s...